The present invention relates generally to connecting rods for coupling crankshafts and pistons and to the techniques for fabricating and assembling such arrangements and more particularly to an improvement in connecting rods of reduced mass and cost.
Connecting rods for coupling pistons and crankshafts may be broadly categorized in two types. The first type referred to herein as a split ring connecting rod is more sophisticated and expensive and may be formed from a wide variety of materials with the ring or portion thereof which surrounds the crankshaft being formed as two split C-shaped halves each containing an inner bearing surface and boltable together, often with shims, in position about the crankshaft. The second type referred to herein as a one piece connecting rod includes an elongated arm portion with enlarged annular portions at the opposite ends thereof and is assembled by passing one of those annular portions over an end of a crankshaft and along the crankshaft into approximate final position with rollers being inserted intermediate the crankshaft and annular portion whereupon the crankshaft is repositioned somewhat to trap the rollers between the annular portion and the crankshaft. The present invention applies exclusively to this second type connecting rod.
Connecting rods of the second type have heretofore exclusively been formed from a steel stamping or forging hardened by a carborizing process and having the inner annular surface which forms the outer crankshaft bearing race ground to form a good bearing surface. Two undesirable features of such known connecting rods of the second type are their expense and their undesirably high mass.
Devices which convert between rotary crankshaft motion and reciprocating piston motion, such as internal combustion engines, compressors, steam engines, and the like, vibrate or shake due to the inertial effects of the internal moving parts. Typically, these inertial effects are only partially counterbalanced with the net result that the vibrations experienced by such machines during operations are determined by the masses of the several internal moving parts with greater mass resulting in greater vibration. Reduction in the mass of a given moving part within such devices may also allow a reduction in counterweight or counterbalancing masses yielding overall vibration reduction which is substantially greater than that due to the reduction in mass of the moving part per se. Thus, a small reduction in mass may result in a substantial reduction in device vibrations.